1. Field of the Invention
The invention relates to an apparatus for use in testing an inverter.
2. Description of the Related Art
In general, in a dispersed power supply system such as a photovoltaic power system, an inverter is used to establish interconnection with an alternating current (AC) power system. In such an inverter, a function for avoiding islanding may be demanded in some cases (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2008-104262).
For example, in the Institute of Electrical and Electronics Engineers (IEEE) 1547 standard, conducting the following islanding test is demanded.
First, to conduct the anti-islanding test, a circuit is configured to interconnect an AC power system with an inverter. An AC load is connected to this circuit so that AC power can be supplied from the AC power system and the inverter. This AC load is set such that inductance and capacitance thereof have the same value. Then, electric power is supplied to the AC load by parallel operations of the AC power system and the inverter, whereby the AC load is caused to resonate. In this resonating state, the AC power system is disconnected from the circuit, and islanding of the inverter is allowed. At this time, the inverter solely supplies electric power to the AC load. In this anti-islanding test, it is confirmed that the inverter is automatically stopped in such an islanding state.
However, a capacity of the AC load provided to conduct the above-described test must be increased as a capacity of the inverter as a test target is raised. Therefore, when the inverter is large, the AC load is also large.